It is only possible to obtain analytical results that are suitable for their intended purpose if the equipment used is capable of producing measurements of the required quality. To ensure that this requirement is met, analysts should define the performance criteria required from the instruments, ensure that only suitable instruments are selected for analytical measurements, and confirm that these instruments continue to meet these criteria for their entire operational life. This process should be conducted on a formal, documented basis, known as equipment qualification. In addition to describing the key elements of equipment qualification for all analytical instruments, this paper gives specific guidance on its application to conductivity systems that has never previously appeared in the literature. The benefits of performing equipment qualification are highlighted and guidance is given on the selection of control standards and why the equipment vendor performing stages of equipment qualification can be of benefit to the user. The relationship between equipment qualification and method validation is discussed, including how these activities play a major role in determining the quality control measures that should be applied to routine analysis.